Sc Link system Cold powering cooldown warmup requirements

Sc Link system Cold powering cooldown & warmup requirements Jerome Fleiter, Amalia Ballarino 9 Feb 2021 Meeting #1 1

Sc Link system Cold powering cooldown & warmup requirements § Controlled cool down and warm up sequences for HL LHC machine are required for Sc Link system in order to avoid excessive thermal shock and possible mechanical damages on the cable system. § For DEMO 1, 2 and 3 we controlled the mass flow (1 -3 g/s) and the delta T (~60 K) during all the phases of the cool down and warm up (see next slides). § The mass flow and delta T where interlocked to interrupt the sequence if thermal or mass flow run away. 2

Cryo infrastructure of DEMO 3

1 st Cool down of DEMO 2 § § PDT 802 range 0 -10 mbar Out of range during cool down Mass flow increased progressively from 2 g/s to 4. 4 g/s Interlocks on ∆T stopped CD two times PDT 802 back in range once cold 4

1 st Warm up of DEMO 2 § Controlled d. T during warm up with mass floe of 0. 5 g/s § DEMO 2 in “floating mode” as from 25 th of June (stop of cold box): § No mass flow § No control of delta T § Warm up only on heat in leak § Warm up completed after recovery of cold box 5

Cool down of DEMO 3 6

Warm up of DEMO 3 7

Sc Link system Cold powering cooldown & warmup requirements § For the machine operation direct control of delta T of GHe across the Sc Link is not foreseen at the moment. § But indirect control could be applied to limit thermal shock applied to the Sc Link system: § If the cryo lines are progressively cooled down and warmed up, we could benefit from this long thermal cycle of the lines. § If the cryo lines are assumed cold (4 K) or warm (300 K) for respectively the cool down and warm up, we could have a tiny mass flow (0. 2 -0. 5 g/s) that we modulate in order to not exceed a predetermined delta T. § If indirect control is not adequate, dedicated GHe controlled temperature systems will be required. 8

Sc Link system Cold powering cooldown & warmup requirements § In order to better define the cool down sequences, we will need to identify which type of cycles we have to perform: (technical stop, LS, …), and which are the boundaries (time, and temperature at interfaces) § For each identified sequence we will need to know the temperature profile vs time of GHe in the feeding line in order to adapt the strategy to control thermal gradient during the cool down/warm up sequence. 9